fix: rename page_size_kib to page_size

CHANGELOG.md

@@ -24,6 +24,13 @@ and this project adheres to
 
 ### Deprecated
 
+- [#4948](https://github.com/firecracker-microvm/firecracker/pull/4948):
+  Deprecated the `page_size_kib` field in the
+  [UFFD handshake](docs/snapshotting/handling-page-faults-on-snapshot-resume.md#registering-memory-to-be-handled-via-userfault-file-descriptors),
+  and replaced it with a `page_size` field. The `page_size_kib` field is
+  misnamed, as the value Firecracker sets it to is actually the page size in
+  _bytes_, not KiB. It will be removed in Firecracker 2.0.
+
 ### Removed
 
 ### Fixed

src/firecracker/examples/uffd/uffd_utils.rs

@@ -32,7 +32,7 @@ pub struct GuestRegionUffdMapping {
     /// Offset in the backend file/buffer where the region contents are.
     pub offset: u64,
     /// The configured page size for this memory region.
-    pub page_size_kib: usize,
+    pub page_size: usize,
 }
 
 impl GuestRegionUffdMapping {
@@ -79,7 +79,7 @@ impl UffdHandler {
                 mappings.len()
             )
         });
-        let page_size = first_mapping.page_size_kib;
+        let page_size = first_mapping.page_size;
 
         // Make sure memory size matches backing data size.
         assert_eq!(memsize, size);
@@ -152,10 +152,7 @@ impl UffdHandler {
                     return false;
                 }
                 Err(Error::CopyFailed(errno))
-                    if std::io::Error::from(errno).raw_os_error().unwrap() == libc::EEXIST =>
-                {
-                    ()
-                }
+                    if std::io::Error::from(errno).raw_os_error().unwrap() == libc::EEXIST => {}
                 Err(e) => {
                     panic!("Uffd copy failed: {e:?}");
                 }
@@ -364,7 +361,7 @@ mod tests {
             base_host_virt_addr: 0,
             size: 0x1000,
             offset: 0,
-            page_size_kib: 4096,
+            page_size: 4096,
         }];
         let dummy_memory_region_json = serde_json::to_string(&dummy_memory_region).unwrap();
 
@@ -397,7 +394,7 @@ mod tests {
             base_host_virt_addr: 0,
             size: 0,
             offset: 0,
-            page_size_kib: 4096,
+            page_size: 4096,
         }];
         let error_memory_region_json = serde_json::to_string(&error_memory_region).unwrap();
         stream

src/vmm/src/persist.rs

@@ -108,6 +108,11 @@ pub struct GuestRegionUffdMapping {
     /// Offset in the backend file/buffer where the region contents are.
     pub offset: u64,
     /// The configured page size for this memory region.
+    pub page_size: usize,
+    /// The configured page size **in bytes** for this memory region. The name is
+    /// wrong but cannot be changed due to being API, so this field is deprecated,
+    /// to be removed in 2.0.
+    #[deprecated]
     pub page_size_kib: usize,
 }
 
@@ -593,11 +598,13 @@ fn create_guest_memory(
     let mut backend_mappings = Vec::with_capacity(guest_memory.num_regions());
     let mut offset = 0;
     for mem_region in guest_memory.iter() {
+        #[allow(deprecated)]
         backend_mappings.push(GuestRegionUffdMapping {
             base_host_virt_addr: mem_region.as_ptr() as u64,
             size: mem_region.size(),
             offset,
-            page_size_kib: huge_pages.page_size_kib(),
+            page_size: huge_pages.page_size(),
+            page_size_kib: huge_pages.page_size(),
         });
         offset += mem_region.size() as u64;
     }
@@ -788,26 +795,26 @@ mod tests {
         assert_eq!(uffd_regions.len(), 1);
         assert_eq!(uffd_regions[0].size, 0x20000);
         assert_eq!(uffd_regions[0].offset, 0);
-        assert_eq!(
-            uffd_regions[0].page_size_kib,
-            HugePageConfig::None.page_size_kib()
-        );
+        assert_eq!(uffd_regions[0].page_size, HugePageConfig::None.page_size());
     }
 
     #[test]
     fn test_send_uffd_handshake() {
+        #[allow(deprecated)]
         let uffd_regions = vec![
             GuestRegionUffdMapping {
                 base_host_virt_addr: 0,
                 size: 0x100000,
                 offset: 0,
-                page_size_kib: HugePageConfig::None.page_size_kib(),
+                page_size: HugePageConfig::None.page_size(),
+                page_size_kib: HugePageConfig::None.page_size(),
             },
             GuestRegionUffdMapping {
                 base_host_virt_addr: 0x100000,
                 size: 0x200000,
                 offset: 0,
-                page_size_kib: HugePageConfig::Hugetlbfs2M.page_size_kib(),
+                page_size: HugePageConfig::Hugetlbfs2M.page_size(),
+                page_size_kib: HugePageConfig::Hugetlbfs2M.page_size(),
             },
         ];
 

src/vmm/src/vmm_config/machine_config.rs

@@ -71,8 +71,8 @@ impl HugePageConfig {
         matches!(self, HugePageConfig::Hugetlbfs2M)
     }
 
-    /// Gets the page size in KiB of this [`HugePageConfig`].
-    pub fn page_size_kib(&self) -> usize {
+    /// Gets the page size in bytes of this [`HugePageConfig`].
+    pub fn page_size(&self) -> usize {
         match self {
             HugePageConfig::None => 4096,
             HugePageConfig::Hugetlbfs2M => 2 * 1024 * 1024,